Bible Notes Online - Joshua 20 - ESV
Commentary

v1-3: Joshua had instructions to set aside six cities of refuge, for those who accidentally killed someone. This highlights two important details:

- the nuance; a difference between murder and manslaughter. The law sought to delinate between those offences.

- God's mercy, that a person who had not intended to take a life, would not be put to death.

v4-6: The 'guilty' man had to present his case upon arrival at the city. His pursuers would have an opportunity to put their case also.

v7-9: The cities were set out so that an Israelite could conveniently reach one. No one, apart from those living in the extreme south (the desert) was more than about 50 miles from any of them (my estimate).

The cities west of the Jordan were all on mountains; a city set on a hill cannot be hidden.

Each of the cities belonged to the Levites; 21.13, 21, 27, 32, 36, 38; thus Levites were present to rule on any case that arose.

The cities point us to Jesus Christ, to whom we flee for refuge. There is safety from the avenger of blood, the law, before which would be guilty, and worthy of death.